At a vehicle manufacture site, an occurrence of an accident commonly due to pedestrian walking or standing at a dangerous region and being injured by a vehicle that carries cargo (i.e., cargo vehicle). Because of special design of the cargo vehicle, a driver cannot see the pedestrians in front the cargo vehicle when the cargo vehicle is loaded. Further, an accident may occur if a pedestrian is located within a machine operation area. Therefore, an alert system is commonly installed at a workplace to warn the workers of oncoming risk situation.
For example, the U.S. Pat. No. 6,232,877 discloses a warning system to alert a user of an approaching vehicle to prevent an accident. The alert system includes a receiver disposed on a safety vest or a shoe, an emitter and a processor installed on the vehicle. The processor receives a signal and processes the signal to provide information to alert the user. The safety vest includes a vibrator that alerts the user by vibrating when triggered. The safety vest includes a microphone or a horn that may be activated when receiving a signal emitted from the emitter. Thus, the alert system warns the worker located at a remote distance about the oncoming danger. However, the warning systems in the existing technologies only calculate an actual spatial distance of a person (i.e., an actual distance to a vehicle and a dangerous object) via signal emitter and receiver. These methods or systems cannot track and identify a relative position between the person and dangerous objects or dangerous area in real time, and thus it may not be easy to prevent an occurrence of an accident and may not be easy to identify responsibility after the accident.